March 24, 2012: Smoke is released into the sky at a refinery in Wilmington, California. (Reuters)

The Republican head of the House science committee is fighting to obtain documents from the Obama administration on a controversial global warming study, as the agency that produced it locks down internal records despite a subpoena.

The report by the National Oceanic and Atmospheric Administration (NOAA) claims to refute prior studies showing the rate of global warming had flattened in recent decades.

Rep. Lamar Smith, R-Texas, a global warming skeptic who questioned the data, issued a subpoena on Oct. 13 for the agency to "compel production of documents and communications relating to adjustments of historical temperature data."

But the chairman of the Committee on Science, Space and Technology complained this week that the agency still is only providing some of the documents.

“The American people have every right to be suspicious when NOAA alters data to get the politically correct results they want and then refuses to reveal how those decisions were made," Smith said in a statement. "NOAA needs to come clean about why they altered the data to get the results they needed to advance this administration's extreme climate change agenda.”

The NOAA says it has provided all necessary documents and data as well as multiple in-person briefings -- but made clear it does not plan to provide the private communications of scientists due to a long-standing practice in the scientific community of keeping such information private in order to encourage open discussion.

Smith's committee says it does not recognize the confidentiality interest as a legitimate exemption, and still wants communications between NOAA employees. A committee aide told FoxNews.com the subpoena was not just about communication between scientists, but the entire decision-making process behind the report.

“These are government employees using government email making decisions that have potentially far-reaching implications and it’s the committee’s role to understand the full context of that decision-making process,” the aide said.

Underlying Smith's quest for records is a suspicion that the agency's study was politically influenced. But the agency denies that outright.

"There is no truth to the claim that the study was politically motivated or conducted to advance an agenda. The published findings are the result of scientists simply doing their job -- ensuring the best possible representation of historical global temperature trends is available to inform decision makers, including the U.S. Congress,” NOAA spokeswoman Ciaran Clayton told FoxNews.com.

The June report said the rate of global warming in the last 15 years has been “as fast or faster than that seen during the latter half of the 20th century.” This contradicted earlier findings.

“The study refutes the notion that there has been a slowdown or 'hiatus' in the rate of global warming in recent years,” the study claimed.

The theory of a 15-year hiatus in global warming has been frequently cited by those skeptical of global warming, and was supported by a report released between 2013 and 2014 by The Intergovernmental Panel on Climate Change (IPCC) that determined the upward global surface temperature trend from 1998-2012 was lower than from 1951-2012.

However, NOAA used not only data from 2013 and 2014, but also introduced what it called “improved versions of both sea surface temperature and land surface air temperature datasets” and in doing so concluded global warming has continued to accelerate upward.

"This study, led by a renowned climate scientist, was independently peer reviewed and vetted by a well regarded scientific journal,” Clayton said, adding that the study was not undertaken to disprove the “hiatus” theory. The study was published in 'Science' and was conducted by Tom Karl, Director of NOAA's National Centers for Environmental Information.

Democrats on the House committee were not supportive of Smith, accusing him of “furthering a fishing expedition, rather than engaging in focused oversight with a legitimate goal in mind.”

“It saddens me that the Chairman’s aggressive oversight this Congress seems designed to generate press releases and harass the Executive than to actually discover any significant waste, fraud or abuse in the programs we oversee,” Rep. Eddie Bernice Johnson, D-Texas, said in an Oct. 23 letter.

“[W]e won’t be complicit in the illegitimate harassment of our Nation’s research scientists,” Johnson said.

However, Smith has pledged to continue his investigation.

“The agency has yet to identify any legal basis for withholding these documents. The Committee intends to use all tools at its disposal to undertake its Constitutionally-mandated oversight responsibilities,” Smith said in a statement.

Adam Shaw is a reporter covering U.S. and European politics for Fox News.. He can be reached here.